Morris Minor Owners Club

I want to fit an oil gauge and I am assuming there is not really any point having an oil warning light as well, the gauge will tell me more than the light can anyway. Can anyone tell me the thread type and size where the oil pressure switch is fitted so I can get the correct connector. Some of the gauges come with a range of fittings so I want to check the ones supplied before purchase in case I have to buy the correct one.

Use a T piece and keep the light. It will draw your eye better than a gauge. http://www.ebay.co.uk/itm/Classic-Mini- ... 2c9a24b876

I retro-fitted a 20psi oil pressure switch+light on my MG and a buzzer rather than just having the gauge.
Regards
Declan[frame][/frame]

I kept my light when I fitted my gauge, at least when you start the engine before the gauge rises, you can see the light go out as the pressure rises which is reassuring.

Thank you for the reply's so far but the question remains what is the tread type and size for the oil pressure switch.

1/8" NPT. A Mini T piece will fit so you cant fit the gauge and your pressure switch.

Ah, that's what I needed to know. Thank you all for your replies.

There's a very handy list at the top of the Mechanical section, it gives most of the thread sizes on the car

NPT is American - I would be surprised.... I think it is BSPT. Just get the T piece I indicated from ebay - it WILL fit and make the job very simple.

I tried a 1/8" BSP nipple and T piece in the connection but it wouldn't screw in more than a thread but as you say the Mini T pieces are perfect.

It has to be BSPT (T = tapered)........

As BMC says you need a t-piece. I got this one from minispares and a braided hose as seemed more robust than a plastic pipe.
http://www.minispares.com/product/Class ... |Back%20to
Loads of places to get them from, worth getting a few spare fibre washers in case you lose one during installation.

It was a BSP tapered thread, didn't fit.

Is the adapter 1/8" BSPT or NPT? We had this discussion while I was putting the thread chart together, and I was sure at the time that it is BSPT, but the conclusion then was that it is NPT. Bit odd, but true!

The difference between the two is the thread angle (55° for BSPT and 60° for NPT) and the thread pitch (28tpi BSPT and 27tpi NPT).

BSP threads can be either parallel (BSPP) or tapered (BSPT), whereas NPT threads are only tapered, so no additional distinction is needed.

G'day all
American pipe threads can be either tapered or parallel. See attached link.
Cheers Bob
https://forums.autodesk.com/autodesk/at ... AMSTPT.pdf

I find it hard to believe American size would be used in UK..... And these gauges/adapters/T pieces are pretty much universal across all makes of UK produced cars.

The thread is as Richard says 1/8" x 27 TPI NPT.

The Smiths oil pressure switch in the attached photo has a parallel threads whilst the male and female threads of the adapter have tapered threads.

The tap screwed into the adapter is a tapered 1/8" x 27 TPI NPT one.

Oil pressure switch threads can come with either parallel or tapered threads.[frame][/frame]

Both types of oil pressure switch can be used in the taper female threads but a bit of care must be used when tightening the parallel thread type into the tapered thread adapter.

The 1/8" BSP thread has 28 TPI.

You will also need a male - female adapter when using the 'T' adapter.[frame][/frame]

Hi Phil and all
The importment thing to be aware of is the fact that ANP parallel threads are designed to do the same job as BSP parallel threads, and that is to provide axial compression to the sealing medium, whether it be copper or fibre washer, Dowty seal, 'O' ring or what ever. The issue seems to be complicated by the use of a a parallel form of a pipe thread to do this when another 'standard' thread could be used.
Cheers Bob

Here is an oil pressure switch with a tapered thread.
I am afraid we are stuck with what we can get and whilst it would be nice to have either parallel male/female threads or tapered male/female threads it is not always possible to get the ideal combination so have to make the best of a bad bargin.
Phil[frame][/frame]

Well researched Phil -I don't have access to taps in these sizes - so I just use what comes from the suppliers and never had any problems. I still think it's strange American threads would be used....but hey ho -the evidence is there!